1. Field of the Invention
The present invention generally relates to digital voice communications systems and, more particularly, to integrated control and signal processing functions in a cellular telephone.
2. Description of the Prior Art
A digital cellular subscriber unit contains functions such as voice coding, modem and equalization, that are implemented by a digital signal processor (DSP) chip, and control functions such as call processing, user interface and the like that are implemented by a separate microcontroller. The logic behind the common practice of using a microcontroller to implement control functions is that these functions do not need a very fast central processor unit (CPU) like a DSP but need a lot of code space, usually written in a high level language, and are prone to many modifications during the software development and maintenance cycle. A DSP chip architecture is more suitable to implement DSP algorithms, such as digital filtering. Since those algorithms are CPU intensive, they are usually written in assembly language.